A typical LCD has the advantages of portability, low power consumption, and low radiation. LCDs have been widely used in various portable information products, such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the LCD is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
FIG. 2 is essentially an abbreviated circuit diagram of a typical LCD 100. The LCD 100 includes an LCD panel 110, a number of data driving circuits 130, and a number of gate driving circuits 150. The LCD panel 110 includes a first substrate (not shown), a second substrate (not shown) arranged parallel to the first substrate, and a liquid crystal layer (not shown) sandwiched between the first substrate and the second substrate. Liquid crystal material of the liquid crystal layer has anisotropic transmittance.
The first substrate includes a number of gate lines 112 that are parallel to each other and that each extend along a first direction, and a number of data lines 114 that are parallel to each other and that each extend along a second direction orthogonal to the first direction. The intersecting gate lines 112 and data lines 114 define a number of pixel units 120 therebetween. The first substrate also includes a number of thin film transistors (TFTs) 116 that function as switching elements, and a number of pixel electrodes 118. Each TFT 116 is provided in a respective pixel unit 120, in the vicinity of a respective point of intersection of the gate lines 112 and the data lines 114.
The second substrate includes a number of common electrodes 119 generally opposite to the pixel electrodes 118. In particular, the common electrodes 119 are formed on a surface of the second substrate nearest to the first substrate, and are made from a transparent material such as ITO (Indium-Tin Oxide) and the like.
FIG. 3 is an equivalent circuit diagram of one pixel unit 120 of the LCD 100. A gate electrode 1162, a source electrode 1163, and a drain electrode 1164 of the TFT 116 are connected to the corresponding gate line 112, the corresponding data line 114, and a corresponding pixel electrode 118 respectively. Liquid crystal material sandwiched between the pixel electrode 118 and the corresponding common electrode 119 on the second substrate (not shown) is represented as a liquid crystal capacitor Clc. Csd is a parasitic capacitor formed between the source electrode 1163 and the drain electrode 1164 of the TFT 116. “R” represents an essential resistance of the data line 114.
When the LCD 100 works, in each pixel unit 120, a scanning signal generated by a corresponding one of the gate driving circuits 150 is provided to the gate electrode 1162 of the TFT 116. Thus the TFT 116 is switched on. At the same time, gradation voltage generated by a corresponding one of the data driving circuits 130 is provided to the pixel electrode 118 via the corresponding data line 114 and the activated TFT 116 in series.
Because the essential resistance “R” of the data line 114 and the parasitic capacitor Csd form a resistance-capacitance (RC) delay circuit (not labeled), the gradation voltage transmitted on the data line 114 is delayed and reduced by the RC delay circuit, as shown in FIG. 4. Vd1 represents the gradation voltage on a point of one of the data line 114 that is near one of the gate driving circuits 130, and Vd2 represents the gradation voltage on another point of the same data line 114 that is far from the gate driving circuit 130. As seen, the gradation voltage Vd2 is delayed compared to the gradation voltage Vd1. The delay of the gradation voltage is determined by the essential resistance “R” of the data line 114 and the capacitance of the parasitic capacitor Csd. When the size of the display screen of the LCD 100 is large, the signal delay of the gradation voltage becomes correspondingly longer. Since the gradation voltage provided to the pixel unit 120 far from the gate driving circuit 130 is partly delayed by the RC delay circuit, the brightness of the LCD 100 far from the gate driving circuit 130 is correspondingly reduced. That is, the brightness of the LCD 100 is nonuniform, and the quality of images displayed by the LCD 100 may be unsatisfactory.
It is desired to provide an LCD which can overcome the above-described deficiencies.